QTableWidget修改表头颜色的代码为什么只在QMainWindow中有效？-服务报错

"<span style=""widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;display:inline !important;font:14px/21px Arial;white-space:normal;orphans:2;float:none;letter-spacing:normal;color:#333333;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;""> 最近做项目用到了QTableWidget，基于QWidget做的，QTableWidget的 <span style=""border-bottom:#fa891b 1px solid;widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;outline-style:none;font:14px/21px Arial;white-space:normal;orphans:2;letter-spacing:normal;color:#333333;cursor:pointer;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">背景色 <span style=""widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;display:inline !important;font:14px/21px Arial;white-space:normal;orphans:2;float:none;letter-spacing:normal;color:#333333;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">，背景 <span style=""border-bottom:#fa891b 1px solid;widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;outline-style:none;font:14px/21px Arial;white-space:normal;orphans:2;letter-spacing:normal;color:#333333;cursor:pointer;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">图片 <span style=""widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;display:inline !important;font:14px/21px Arial;white-space:normal;orphans:2;float:none;letter-spacing:normal;color:#333333;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">，文字 <span style=""border-bottom:#fa891b 1px solid;widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;outline-style:none;font:14px/21px Arial;white-space:normal;orphans:2;letter-spacing:normal;color:#333333;cursor:pointer;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">颜色 <span style=""widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;display:inline !important;font:14px/21px Arial;white-space:normal;orphans:2;float:none;letter-spacing:normal;color:#333333;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">都可以改变，表头的 <span style=""border-bottom:#fa891b 1px solid;widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;outline-style:none;font:14px/21px Arial;white-space:normal;orphans:2;letter-spacing:normal;color:#333333;cursor:pointer;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">字体 <span style=""widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;display:inline !important;font:14px/21px Arial;white-space:normal;orphans:2;float:none;letter-spacing:normal;color:#333333;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">颜色也可以改变，但是表头的颜色不能改变，在论坛看了很多高手的回答，无论是获取表头对象设置还是使用样式表设置都没效果。本来以为是不是代码无效，就做了三个demo来验证，分别是基于QMainWindow,QDialog,QWidget.只有QMainWindow中的代码实现了效果， <span style=""border-bottom:#fa891b 1px solid;widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;outline-style:none;font:14px/21px Arial;white-space:normal;orphans:2;letter-spacing:normal;color:#333333;cursor:pointer;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">其他 <span style=""widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;display:inline !important;font:14px/21px Arial;white-space:normal;orphans:2;float:none;letter-spacing:normal;color:#333333;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">两个都无效，求解啊？ <img src=""http://www.qtcn.org/bbs/images/post/smile/wangwang/20.gif"" />



<span style=""widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;display:inline !important;font:14px/21px Arial;white-space:normal;orphans:2;float:none;letter-spacing:normal;color:#333333;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">QTableWidgetItem *columnHeaderItem0 = ui->tableWidget->horizontalHeaderItem(i); //获得水平方向表头的Item对象
<span style=""widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;display:inline !important;font:14px/21px Arial;white-space:normal;orphans:2;float:none;letter-spacing:normal;color:#333333;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">columnHeaderItem0->setFont(QFont("Helvetica")); //设置字体
<span style=""widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;display:inline !important;font:14px/21px Arial;white-space:normal;orphans:2;float:none;letter-spacing:normal;color:#333333;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">columnHeaderItem0->setBackgroundColor(QColor(13, 13, 13));  //设置 <span style=""border-bottom:#fa891b 1px solid;widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;outline-style:none;font:14px/21px Arial;white-space:normal;orphans:2;letter-spacing:normal;color:#333333;cursor:pointer;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">单元格 <span style=""widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;display:inline !important;font:14px/21px Arial;white-space:normal;orphans:2;float:none;letter-spacing:normal;color:#333333;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">背景颜色
<span style=""widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;display:inline !important;font:14px/21px Arial;white-space:normal;orphans:2;float:none;letter-spacing:normal;color:#333333;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">columnHeaderItem0->setTextColor(QColor(233, 233, 233)); //设置文字颜色


<span style=""widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;display:inline !important;font:14px/21px Arial;white-space:normal;orphans:2;float:none;letter-spacing:normal;color:#333333;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;"">————————————————————————————————————————————————


<span style=""widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;outline-style:none;font:14px/21px Arial;white-space:normal;orphans:2;letter-spacing:normal;color:#333333;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;""><span style=""outline-style:none;color:#333333;""><span style=""line-height:1.5em;outline-style:none;font-family:'Arial ';"">ui->tableWidget->horizontalHeader()->setStyleSheet("border:2px groove gray;border-radius:10px;padding:2px 4px;background-color: rgb(170, 170, 255);font: 20pt '华文隶书';");
<span style=""widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;outline-style:none;font:14px/21px Arial;white-space:normal;orphans:2;letter-spacing:normal;color:#333333;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;""><span style=""outline-style:none;color:#333333;""><span style=""line-height:1.5em;outline-style:none;font-family:'Arial ';"">

<span style=""widows:2;text-transform:none;background-color:#ffffff;text-indent:0px;outline-style:none;font:14px/21px Arial;white-space:normal;orphans:2;letter-spacing:normal;color:#333333;word-spacing:0px;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px;""><span style=""outline-style:none;color:#333333;""><span style=""line-height:1.5em;outline-style:none;font-family:'Arial ';""><span style=""outline-style:none;font-size:12px;""><span style=""outline-style:none;display:inline-block;""><img src=""http://www.qtcn.org/bbs/attachment/Mon_1207/17_133462_35dd893c7f681d8.jpg?14"" /><span style=""outline-style:none;font-size:12px;""><span style=""outline-style:none;display:inline-block;""><img src=""http://www.qtcn.org/bbs/attachment/Mon_1207/17_133462_6d9a8d9eadbfa3b.jpg?13"" />"